Simon @ SciToys show you how to make a DIY digital thermometer a multimeter, LM34 / LM35 ICs, 180k ohm resistor, and a 9V battery – “With the easy availability of inexpensive digital multimeters, and integrated circuit temperature sensors, it is now very easy to build a sensitive and accurate digital thermometer that can be used for many experiments around the house or in the amateur laboratory.

There are two tenperature sensors that make this particulary easy — the LM34 and the LM35. These are callibrated in Fahrenheit and Celsius respectively, and when read by the meter, they produce ten millivolts per degree in their respective scales, so the meter can be directly read in temperatures, down to a tenth of a degree. “ – Link.